Many growth factors and hormones such as nerve growth factor (NGF), platelet derived growth factor (PDGF), epidermal growth factor (EGF) and insulin mediate their signals through interactions with cell surface tyrosine kinase receptors. The transduction of extracellular signals across the membrane, initiated by ligand binding, leads to the propagation of multiple signaling events which ultimately control target biochemical pathways within the cell.
The phosphatidylinositol 3-kinases (PI3Ks) represent a ubiquitous family of heterodimeric lipid kinases that are found in association with the cytoplasmic domain of hormone and growth factor receptors and oncogene products. PI3Ks act as downstream effectors of these receptors, are recruited upon receptor stimulation and mediate the activation of second messenger signaling pathways through the production of phosphorylated derivatives of inositol (Fry, Biochim. Biophys. Acta., 1994, 1226, 237-268). PI3Ks have been implicated in many cellular activities including growth factor mediated cell transformation, mitogenesis, protein trafficking, cell survival and proliferation, DNA synthesis, apoptosis, neurite outgrowth and insulin-stimulated glucose transport reviewed in (Fry, Biochim. Biophys. Acta., 1994, 1226, 237-268).
The PI3-kinase enzyme heterodimers most commonly consist of a 110 kD (p110) catalytic subunit associated with an 85 kD (p85) regulatory subunit. Recently however, three smaller regulatory subunits have been identified, two 55 kD subunits (p55.alpha. and p55.gamma.) and one 50 kD subunit (p50.alpha.) (Shin et al., Biochem. Biophys. Res. Commun., 1998, 246, 313-319).
The PI3 kinase p55 gamma regulatory subunit (also known as hp55.gamma., p55.gamma., PIK3R3 and p55PIK) was identified from a human fetal brain library using a two-hybrid system to identify proteins that interact with the tyrosine kinase family of receptors. Like its 85 kD counterpart, PI3 kinase p55 gamma was shown to interact with both the insulin receptor (IR) and the insulin-like growth factor receptor (IGFIR) (Dey et al., Gene, 1998, 209, 175-183), two receptors that have been shown to play important roles in growth, differentiation and apoptosis.
Four distinct mRNA species of PI3 kinase p55 gamma were found to be expressed in human adult tissues, including the brain, with the highest levels of expression being in the adult testis. Fetal tissues, however, expressed only the larger mRNA, suggesting the developmental regulation of the PI3 kinase p55 gamma subunit (Dey et al., Gene, 1998, 209, 175-183; Shin et al., Biochem. Biophys. Res. Commun., 1998, 246, 313-319). The isolated splice variants differ from the parent molecule in that one has a 36 amino acid deletion in the N-terminus of the protein and the other contains a 59 amino acid insertion between the SH2 domains of the protein (Dey et al., Gene, 1998, 209, 175-183).
Currently, there are no known therapeutic agents which effectively inhibit the synthesis of the PI3 kinase p55 gamma. Consequently, there remains a long felt need for agents capable of inhibiting PI3 kinase p55 gamma function.
Antisense technology is emerging as an effective means for reducing the expression of specific gene products and may therefore prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications for the modulation of PI3 kinase p55 gamma expression.
The present invention provides compositions and methods for modulating PI3 kinase p55 gamma expression, including modulation of the alternatively spliced forms of PI3 kinase p55 gamma.